Asphalt and method for producing same



Patented Mar. 16, 1943 Donald E. Carr and Harold W. Ritchey, Los Angeles, Calif., assignors to Union Oil Company of California, Los Angeles, Calii'., a corporation oi California No Drawing. Application June 16, 1939, Serial No. 279,490

13 Claims. (01. 106-278) This invention relates to an improved coating or air-blown asphalt and to a process for manufacturing the same.

It is well recognized in the art of manufacturing air-blown, i. e. oxidized or coating type asphalts, that these products may be prepared by blowing the charging stock, such as asphalt residue. produced from asphalt-containing crude oils, with air or other oxygen-containing gases at an elevated temperature. The product resulting from this operation will possess desirable low temperature susceptibilities; a higher melting point for a given penetration as compared with unoxidized asphalts and a moderately high ductility. This type of asphalt is generally preferred in the roofing industry.

In recent years, attention has been focused on the light-promoted oxidation of asphalt and as a result of many roof failures, the Minnesota Mining and Manufacturing Company has investigated the efiect of light and moisture on asphalt and has devised what is now known as the photosensitivity test. They found that under certain degrees of exposure to light, all asphalts form a thin surface coating of oxidized materials, and that by immersing the exposed asphalt in warm water, the degree of oxidation can be strikingly shown by a color change. Sufilciently oxidized surfaces take on a yellow, paint-like appearance, which has been termed rust. The length of exposure necessary to develop this rust is taken as an indication of the degree of photosensitivity of the asphalt.

The work of the above Minnesota company was mainly concerned with the loss of adhesiveness of the asphalt for roofing granules in the case of roll roofing or asphalt shingles in which the surfaces are coated with mineral granules which may transmit a certain amount of light. Surface oxidation of the asphalt in the presence of light was assumed by them to correspond to a loss of binding power for the granules. Asphalts which thus show a high degree of photosensitivity according to the photosensitivity test are regarded as unsuitable for use with their granules.

However, an aspect of more serious consequence to the roofing trade in general is the fact that in the light reaction certain acidic watersoluble substances are formed which, if not washed completely off by rain, tend to concengranules in shingle-coated roofs, has nothing whatever to do with the staining due to oil exudation and in fact, is most frequently encountered with certain asphalts which show low stain numbers by the Barber test, which measures the tendency of an asphalt to exude oil.

The fact that the water-soluble portion of these oxidation products is acidic often results in rather extensive corrosion of down spouts, galvanized roof gutters, etc.

Also, it will be noted that the photosensitivity phenomenon has no necessary connectionwith the fundamental weathering behavior of the asphalt. In fact, some of the asphalts which have the longest Weather-Ometer life' are the most photosensitive and conversely, some of the poorest asphalts from a Weather-Ometer. stand-point are the best from a photosensitivity standpoint,

i. e. are the least photosensitive. Thus, some asphalts which are otherwise considered to be good asphalts and have a long Weather-Ometer life have the disadvantage of being very photosensitive. By Weather-Ometer life is meant the life of an asphalt as measured by the test developed by Dr. Strieter of the U. S. Bureau of Standards.

Thus, it is an object of our invention to protrate in dew puddles and leave yellow stains, es-

Ipecially in hot, moist climates. This is a frequent 'sourceof complaint in the case of mopped roofs or built-up roofing. It should be noted that this form of stain, which may also effect the color of sitive asphalts.

We have discovered that asphalts which areotherwise acceptable but which are inferior from a photosensitive standpoint may be made nonphotosensitive or relatively less photosensitive without lessening any of their other desirable properties by adding to the asphalt relatively small amounts of certain classes of materials which we shall refer to hereinafter as inhibitors of photo-oxidation.

We have found a large number of substances which may be added to photosensitive asphalts to inhibit their photo-oxidation characteristics. Compounds that are characterized by polar character, i. e. long hydrocarbon chains terminating in a polar group such as oxygenated groups, nitro groups, sulphonic groups, halogen or aromatic nuclei, have been found to be particularly suitable as inhibitors of photo-oxidation. The

higher straight chain fatty acids such as lauric,

tridecoic, myristic, pentadecoic, palmitic, margaric, stearic, non-decoic, arachidic, eicosoic or eicosanic, behem'c, tricosoic, lignoceric or carnaubic, pentacosoic, cerotic, hexacosoic, carboceric, cctacosoic and montanic acids; also the alcohols derived from the above mentioned higher straight chain fatty acids such as lauryl, oley stearyl, e'tcfalcohols have been found to be particularly active inhibitors of photo-oxidation. Also, the higher straight chain oleflnic acids, such as undecylinic, myristolenic, palmitolinic, olelc, petroselic, erucic, brassidic, nervonic and like olefinic acids may be used as inhibitors of photooxidation. Likewise, the alcohols derived from these oleflnic acids are good inhibitors of photooxidation.

Many of the commercial materials containing the above mentioned compounds are likewise good inhibitors of photo-oxidation. Among these may be mentioned, montan wax, carnauba wax, hydrogenated fish oil acids, acidulated cocoanut oil acids, acidulated shortening oil acids, cottonthe asphalt, the higher the photosensitivity of the asphalt, the greater will be the amount of inhibitor necessary to inhibit its photos'ensitivity. For example, in the case of an extremely photosensitive asphalt such as a low flash point airblown asphalt produced from Santa Maria Valley (California) crude oil, as much as 5% of the inhibitors of photo-oxidation is necessary to inhibit completely rust formation. On the other hand with air-blown asphalt produced from the same crude but from which light oils have been removed, much less inhibitor has been found necessary to obtain an asphalt that is superior to an air-blown asphalt produced from the least photo-sensitive crude oils.

The addition of the inhibitor of photo-oxidation to the asphalt may be made by simply adding the particular material to the asphalt while the latter is in a melted state and agitating the mixture sufllciently to ensure thorough distribution of the material through the asphalt. This may be accomplished at or near the termination of the air-blowing operation while the asphalt is still hot. However, when such inhibitors are used which are not volatile at the elevated alrblowing temperature and which are not reacted upon by the air, such materials may be added before or during the oxidation operation.

While particular emphasis has been placed on the use of inhibitors of photo-oxidation with relatively photo-sensitive air-blown or oxidized asphalts since these asphalts are especially adapted for use in roof coatings and the like, it will be observed that our invention is not restricted. to such asphalts. We may add the foregoing materials to other type of photosensitive asphalts such as asphalt-containing residua or steam blown asphalts or naturally occurring asphalts. We may also add the inhibitors of photooxidation of crude oils or even to oily distillates which are photosensitive such as lubricating oils or insecticidal spray oils.

It is also within the scope of our invention to decrease the photosensitive characteristics of relatively non-photosensitive asphalts by the addition of inhibitors of photo-oxidation whether these asphalts have been air-blow nor otherwise. We ha e found that even in the case of the relatively non-photosensitive asphalts produced from such crude oils as Mid-Continent, Santa Fe Springs and San Joaquin Valley such as Posa Creek, we have been able to lower the photosensitivity of such asphalts to a considerable extent.

The addition of the inhibitor of photo-oxidation may sometimes change the physical characteristics of the original air-blown asphalt such as its melting point and penetration, lowering the melting point and increasing the penetration. However, this is not deleterious and in fact, this change in melting point and penetration usually improves the melting point-penetration relations, imparting greater air-blown characteristics.

The following are submitted as specific examples of the use of inhibitors of photo-oxidation. These, however, are not to be considered as limit ing but merely as illustrative of our invention.

Example 1 A Santa Maria Valley crude oil was topped with steam to produce an asphalt residue having a viscosity of 120 seconds Furol at 210 F. The residue was then air-blown at 400-450" F. to produce an air-blown asphalt having a melting point of 217 F., pentrations of 10 at 32 F., 17 at 77 F. and 34 at 115 F., a ductility of 3.9 at 77 F., a flash point of 410 F. (Pensky-Martens) and a Weather-Ometer life of 105 cycles. An aluminum panel was coated to a thickness of 0.025 inch with this asphalt. The coated panel was then exposed to the radiation of a 1500 watt lamp at a distance of about 6 inches from the lamp. The I panel was exposed for eight hours at which time it was immersed in warm water at 140 F. resulting in the formation of alight rust. or dulling on the surface of the coating which remained upon drying the panel. The panel was then exposed to the light for an additional four hour period at which time its immersion in the warm water resulted in the formation of a heavy rust which also remained upon drying.

Approximately 5% by weight of montan wax was then incorporated into a portion of the above mentioned air-blown asphalt by mixing the montan wax in the asphalt at a temperature of about 300 F. An aluminum panel was coated as above with this treated asphalt and upon a similar exposure to the aforesaid lamp for thirty-two hours showed no evidence of forming rust when it was immersed in the warm water and dried.

In order to compare the photosensitivity of the above asphalt containing 5% by weight of montan wax with an asphalt produced from a relatively non-photosensitive crude, a Mid-Continent asphalt was air-blown at 400-450" I". to produce an air-blown asphalt having the same physical characteristics as-the aforementioned airblown asphalt produced from Santa Maria Valley crude oil. An aluminum panel was coated with this asphalt to a thickness of 0.025 inch and the coated panel was subjected to the photosensitive test as above. The exposure of the panel to the light showed the formation of a light rust between about thirty-two and thirty-six hours of exposure to the lamp.

Example 2 stanti'ally'the same non-photosensitive characteristics as the above asphalt containing montan wax.

Example 3 An Orcutt (California) crude oil asphalt residuum having a viscosity of 200 seconds Furol at 210 F. was oxidized with air at a temperature of 400-450" F. to produce an air-blown asphalt having a melting point of 226 F., penetrations of 13 at 32 F., 22 at 77 F. and 35 at 115 F., a ductility of 2.6, a flash point of 435 F. (Pensky- Martens) and a Weather-Ometer life of 55 cycles.

An aluminum panel was coated with this asphalt as in the previous examples and the coated panel was subjected to the aforementioned test. At the end of twenty hours, the exposure to the light and subsequent immersion in the warm water followed by drying, resulted in the forma-' tion of a dull rust on the surface of the asphalt coating.

Approximately 1% by weight of hydrogenated fish oil acids were then incorporated into another portion of the above air-blown asphalt. An aluminum panel was coated with this asphalt and the panel was exposed to the above test. The exposure of the coated panel to the light did not show any evidence of rust formation until the panel had been exposed for a total of about fiftysix hours, whereupon a light rust formed on the surface of the coating.

It will be observed that for determining the melting point and penetration, the following methods outlined by the American Society of Testing Materials were used:

Melting point (ball 81 ring method)--- D36-26 Penetration D- 5-25 The foregoing description of our invention is not to be construed as limiting but only as illustrative of the invention as many variations may be made within the scope of the following claims. We claim:

1. A relatively non-photosensitive asphalt comprising a mixture of a relatively photosensitive asphalt and an organic aliphatic inhibitor of photo-oxidation characterized by a long hydrocarbon chain terminating in an oxygenated group, said relatively photosensitive asphalt being characterized by forming a rust when a 0.025 inch layer of said asphalt is exposed to the light of a 1500 watt lamp at a distance of about 6 inches from the lamp for a period greater than approximately 8 hours and less than approximately 32 hours and subsequently immersed in a bath of water at approximately 140 F.

2. An asphalt as in claim 1, in which said inhibitor of photo-oxidation comprises oleic acid.

3. An asphalt as in claim 1, in which said inhibitor of photo-oxidation comprises montanlc acid.

4. An asphalt as in claim 1, in which said inhibitor of photo-oxidation comprises an oxidized parafiln wax.

5. A relatively non-photosensitive asphalt comprising a mixture of a relatively photosensitive asphalt and a higher straight chain fatty acid,

said relatively photosensitive asphalt being characterized by forming a rust when a 0.025 inch layer of said asphalt is exposed to the light of a 1500 watt lamp at a distance of about 6 inches from the lamp for a period greater than approximately 8 hours and less than approximately 32 hours and subsequently immersed in a bath of water at approximately 140 F.

6. An asphalt as in claim 5, in which said higher straight chain fatty acid comprises oleic acid.

7. An asphalt as in claim 5', in which said higher straight chain fatty acid comprises montanic acid.

8. An asphalt as in claim 5, in which said higher straight chain fatty acid comprises oxidized paraflin wax.

9. A relatively non-photosensitive asphalt comprising a mixture of a relatively photosensitive air-blown asphalt and an organic aliphatic inhibitor of photo-oxidation characterized by a long hydrocarbon chain terminating in an oxygenated group, said relatively photosensitive asphalt being characterized by forming a rust when a 0.025 inch layer of said asphalt is exposed to the light of a 1500 watt lamp at a distance of about 6 inches from the lamp for a period greater than approximately 8 hours and less than approximately 32 hours and subsequently immersed in a bath of water at approximately 140 F.

10. A relatively non-photosensitive air-blown asphalt comprising a mixture of a relatively photosensentive' air-blown asphalt having a melting point of approximately 217 F., penetrations of approximately 10, 17 and 34 at 32, 77 and 115 F.

' respectively, a flash point of approximately 410 F. and a weather-ometer life of approximately cycles and a relatively small amount of a higher "-traight chain fatty acid, said relatively photo-sensitive asphalt being characterized by forming a rust when a 0.025 inch layer of said asphalt is exposed to the light of a 1500 watt lamp at a distance of about 6 inches from the lamp for a period greater than approximately 8 hours and less than approximately 32 hours and' 

